Fundamental safety strategy against severe accidents on prototype sodium-cooled fast reactor

• Published in: Journal of nuclear science and technology Vol. 53; no. 11; pp. 1774 - 1786
• Main Authors: Onoda, Yuichi, Kurisaka, Kenichi, Sakai, Takaaki
• Format: Journal Article
• Language: English
• Published: Tokyo Taylor & Francis 01.11.2016; Taylor & Francis Ltd
• Subjects: accident category; defense in depth; PRA; severe accident; severe accident measures; Sodium-cooled fast reactor
• ISSN: 0022-3131; 1881-1248
• DOI: 10.1080/00223131.2016.1159532

The accident categories of severe accidents (SAs) for prototype sodium-cooled fast reactor (SFR) which need proper measures were investigated through the internal event probabilistic risk assessment (PRA) and event tree analysis for the external event and six accident categories, unprotected loss of flow (ULOF), unprotected transient over power (UTOP), unprotected loss of heat sink (ULOHS), loss of reactor sodium level (LORL), protected loss of heat sink (PLOHS) and station blackout (SBO), were identified. Fundamental safety strategy against these accidents is studied and clearly stated considering the characteristics and existing accident measures of prototype SFR, and concrete measures based on this safety strategy are investigated and organized. The sufficiency of these SA measures is confirmed by comparing the evaluated core damage frequency (CDF) and containment failure frequency (CFF) to the target value, 1×10 −5 and 1×10 −6 per plant operating year, respectively, which were selected based on the IAEA's safety target. However, the target value of CDF and CFF should be satisfied considering all the SAs caused by both internal and external events. External event PRA for prototype SFR is now under evaluation and we set out to satisfy the target value of CDF and CFF considering both internal and external events.